Label sheets are commonly available in various configurations with and without printing thereon. A typical label sheet is a laminate of a paper overlay and an underlying release liner. An adhesive bonds the overlay to the liner in the finished article.
In typical use, information is printed on top of the overlay, and the overlay is then removed from the liner by being peeled therefrom. The peeled away label has exposed adhesive so that it may be pressed against paper or other object for attachment thereto. A typical release liner is coated over one side with liquid silicone to provide a low adhesion surface upon which the overlay is temporarily bonded. The adhesive provides a weak bond between the overlay and the silicone liner which maintains the laminate together until it is desired to remove the overlay from the liner.
More complex label sheets include several labels or decals in the overlay defined by respective perimeter die-cuts which allow removal of individual labels from the liner. The individual labels may be directly adjacent to each other or there may be an intervening label rim or border which remains attached to the liner after the individual labels are peeled away.
A further increase in complexity of the label sheet includes an integral paper form attached to the label portion of the overlay which does not overlie the liner. This type of label sheet may be manufactured using a lap joining method wherein the label and liner laminate is pre-manufactured and lap joined along an edge thereof to the paper form. In another integrated method of manufacture, the entire overlay, including the label and form portions thereof, is separately manufactured in a common sheet and the liner is then bonded below the label portion thereof.
These various label sheets nevertheless use a commonly fabricated release liner which is typically manufactured in large rolls with the silicone in liquid form being applied over the entire surface of the liner paper which is then thermally cured. The large roll of release liner is then cut into individual smaller rolls for use in various label sheet applications as required.
Since the liner is typically manufactured in large rolls, cut to size, and used for various applications, it is not practical or even possible to provide printing on top of the liner and below the silicone surface. This leaves only the front and back sides of the overlay and the back side of the liner as available surfaces for printing, and therefore decreases the potential efficiency of the label sheet. Co-pending application Ser. No. 09/114,434, filed Jul. 13, 1998 addresses this limitation by providing label sheets and form/label combinations wherein a release layer can be formed directly on the liner surface after lamination which permits printing in advance of formation of the release layer.
A problem associated with printing under the release layer is that the print can be seen through the liner. This makes it difficult to read material printed on the back of the liner. This is particularly a problem where variable information is printed on the back of the liner since the location and size of such print can not be predicted with certainty making it difficult to anticipate where images can be applied under the release layer without interference. Another problem associated with printing variable information on the back side of the liner is that many inks do not adhere to the unsiliconized surfaces of the liner. This is especially true for toners used in laser printers and copiers. The highly calendared papers used for liners must be treated with a clear ink receptive coating to accept print.